In recent years, safety support systems for automobiles using millimeter wave radars have been put in practical use, and electric devices used in the systems have been accordingly required to be improved in performance. As a way to make an electric device highly functionally operate, a high frequency characteristic is expected to be added to a printed circuit board. Therefore, development is being actively conducted on printed circuit boards using liquid crystal polymer having a low dielectric constant, a low dielectric dissipation factor, and a low transmission loss on a signal line.
For example, PTL 1 proposes a method for manufacturing a single-sided metal clad laminated body. In the method, a metal foil, an insulating film made of a thermoplastic liquid crystal polymer film, and a separation film are stacked and subjected to thermocompression bonding, and the separation film is then removed.
PTL 2 proposes a method for manufacturing the following liquid crystal polymer film laminated base material. First, a surface of a liquid crystal polymer film is roughened with etching liquid. Next, a base material to be laminated and the liquid crystal polymer film are stacked in a manner that the roughened surface of the film and a surface of the base material are opposed to each other. After that, a thermocompression process is performed to laminate the base material and the film into one body.
However, different from epoxy resins or polyimide resins constituting common substrates, the liquid crystal polymer film has a problem that heat resistance is low. In particular, if rigidity (for example, viscosity and elastic modulus) of a liquid crystal polymer film becomes too low due to a heating temperature at the time of thermocompression molding, air can get in and stay between the liquid crystal polymer film and a metal foil or between the liquid crystal polymer film and a single-sided metal clad laminated board, whereby adhesiveness can be reduced.